With rapid development of the automotive industry, people's requirement for vehicle safety has become increasingly strict. As a key safety component in automotive systems, wheels need to continuously improve their performance quality in order to keep up with the increasingly fierce market competition.
The structure of each part of a wheel plays an important safety role in the driving of a vehicle. A wheel center flange is the key part of connecting the wheel with an automotive transmission main shaft, so each main engine factory has set a high standard for its casting quality and mechanical properties. In order to achieve the strength of use, the wheel center is often designed to be relatively thick. For some European and Japanese models, the thickness will even be more than 60 mm (area A in FIG. 1). An obvious cast hot section is thus formed, which seriously affects the formulation of a process plan and is the most vulnerable part in the production.
At present, for the cooling of the wheel center, the conventional air-cooled structure is still the most common way for many aluminum wheel manufacturers. This technique is easy to control and low in cost, but at the same time, has obvious deficiencies: the compressed air has very small heat capacity and low thermal conductivity, so that the heat concentrated in the wheel center cannot be quickly exported, causing low solidification speed of molten aluminum and defects such as shrinkage will be occur in the interior of the casting; due to the low supercooling degree of air cooling, crystal grains at the wheel center tend to be very large, resulting in a loose structure and low mechanical properties; in addition, the wheel center, as a filling and feeding source of the molten aluminum, is not desired to be solidified prematurely, but needs to be rapidly and forcibly cooled at the later stage of the process, and it is clear that the air cooling cannot meet this requirement. Therefore, how to cool the thick and large hot section of the wheel center, ensure a reasonable solidification interval and complete good sequential solidification is an important issue for many casting craftsmen.
Based on the above analysis, in the face of increasing product quality requirements, the existing technical means have been difficult to meet, so certain optimization and improvement are needed to solve the problem of casting production and improve the forming quality of castings.